The spacers between an insulating glass unit including two or more glass panes are typically constructed of aluminum or hollow steel.
A spacer in the form of a strip with a rectangular cross section which is frequently designated as a “swiggle strip” is described in German Patent Document No. DE 30 02 904 A. The strip is provided with protective films, comes from a delivery drum or reel and is applied to the glass pane by means of an apparatus provided with a turnable head. The strip-like spacer is viscoplastic, strongly adhesive (which is desirable for achieving a gas-tight connection at first with the first glass pane and later with the second glass pane of the insulating glass unit), but has a viscosity which is strongly temperature-dependent.
Recently, substantially less temperature-sensitive elastoplastic spacer strips have been developed on the basis of polyurethane or the like. The strips also have a rectangular cross section, are more stable with respect to dimensions and shape than the so-called “swiggle strip,” include a lamination made of aluminum foil on the outside and are provided on the two narrow sides, designated for gluing with the glass panes, with a factory-made thin coating being made of a strongly adhesive glue. The coating is covered with protective foils until the application is made. A method and an apparatus for applying such a strip onto at least the first glass pane of an insulating glass unit consisting of at least two such glass panes is described in German Patent Document No. DE 102 12 359 A.
A noticeable problem with such a strip is that the adhesive applied to the two narrow sides of the strip is not diffusion-proof to water vapor. The adhesive presumably includes a rapidly polymerizing adhesive lacquer composed of methacrylates. That is why, in current methods, the remaining boundary gap is filled with a sealing mass after the assembly of the insulating glass pane, which mass ensures the mandatory tightness against the diffusion of water vapor, because otherwise water vapor would penetrate the enclosed inner space of the insulating glass pane and would unavoidably lead to the formation of condensate and the uselessness of the pane. Suitable filling masses for the boundary gaps are expensive and are required in large quantities due to the considerable cross section.
In German Patent Application No. 103 50 312.9, a more advantageous method is described which works with the same elastoplastic strip but which is not coated with the adhesive on the two narrow sides. A water-vapor diffusion-proof adhesive, preferably a butyl adhesive, is applied onto the narrow sides of the strip only shortly before its application onto the glass panel. It has been noticed, however, that in contrast to the long known and generally common rigid spacer frames with butyl-coated side surfaces, there may occur, as a result of the limited adhesion forces of the butyl adhesive (especially in the case of strips which are wide in proportion to their thickness or in the case of large pane formats and respective long strips) that the strip applied to the first glass pane will travel at certain locations even prior to the application of the second glass pane and/or during the pressing of the two glass panes into the insulating glass unit. In other words, the strip moves slightly from the defined position. This can lead to visual impairments of the finished insulating glass unit by a “wavy” appearance of the spacer and/or the imprecise rectangular configurations of the corners of the spacer.
There is a desire to use suitable plastic strips instead of metallic spacers for reasons of better heat insulation.